The invention relates to driver image capturing apparatus adapted for use in a vehicle to capture a facial image of a driver of the vehicle. The invention further relates to driver monitoring apparatus employing the driver image capturing apparatus.
In order to detect drowsy or inattentive driving, many safety apparatus have been developed that are adapted to capture a facial image, in particular an eye image, of a car driver and to detect condition of the driver based on the captured image.
Such apparatus perform an image capturing process as described below. An infrared camera is mounted on a dashboard or an instrument panel, or near or inside an interior rear-view mirror. The infrared camera is adapted directly to capture a facial image of a driver in a driver seat by receiving infrared radiation reflected by the driver's face. The infrared radiation is used because it provides stable conditions for image capturing and never dazzles the driver.
However, position of the driver's face depends on the driver's physical constitution and posture and on driver seat adjustments. Accordingly, the foregoing image capturing process requires an infrared camera with a field angle wide enough to cover an entire area where the face of the driver is likely to be positioned. Such camera in turn requires a process for recognizing a facial-image area from the captured image having a wide field angle.
In view of the foregoing, JP H11-304428A has proposed an image capturing apparatus adapted to capture an eye image of a driver from behind the driver through an interior rear-view mirror. The apparatus uses reflection of the driver's eyes on the mirror as properly adjusted and viewed from behind.
However, the prior art apparatus has the following problems.
(i) The apparatus can only be mounted at a limited location. In order to capture a facial image with eyes positioned at the center, the apparatus is required to be mounted on a straight line leading rearward from the rear-view mirror.
(ii) The apparatus partially obstructs a field of rear vision of the driver. Thus, the apparatus prevents the rear-view mirror from fulfilling its primary function of providing the field of rear vision to the driver.
(iii) In order to be prevented from interfering the function of the rear-view mirror, the apparatus needs to be small and to be mounted at a distance as great as possible from the mirror.
(iv) The greater the distance between the apparatus and the mirror, the narrower area of image the apparatus will capture through the mirror. The area is a limited one around the eyes of the driver. Thus, it is difficult to capture an image of facial area other than the eyes. Further, there is an increased possibility that a change in facial position of the driver causes the eyes to be excluded from an image to be captured.
(v) Sight of the apparatus gives the driver an uncomfortable feeling of being watched.
In light of the problems, a feature of the invention is to provide a driver image capturing apparatus ensuring capture of an eye image of a driver in a driver's sheet without obstructing the driver's field of rear vision.